Equine Flu

PLEASE NOTE THAT THIS IS A BRIEF SUMMARY OF THE PUBLICATION “INFLUENZA INFECTIONS” AS ACKNOWLEDGED BELOW AND IS PUBLISHED FOR INFORMATION ONLY. YOU ARE ADVISED TO CONSULT YOUR VETERINARY SURGEON IN THE EVENT OF AN EQUINE INFLUENZA OUTBREAK AND FOLLOW THE VETERINARY SURGEON’S ADVICE

Outbreaks around the world
The equine flu virus is of the same type (type A) which infects man and birds, but of a different strain.  It also differs from man in that it is not seasonal but outbreaks are usually associated with congregations of horses for race meetings, shows, sales, etc.

It was first diagnosed in 1956 in Czechoslovakia and later in Europe and America. There were other outbreaks in 1969 in Europe and one of a different strain in China where 20% of the equines died. Where outbreaks occur in an area for the first time, the effects are the most dramatic. An outbreak in South Africa in 1986 and another in Hong Kong in 1992 disrupted race meetings and in India hundreds of equines died in 1987 during an epidemic. Outbreaks were also reported in the Philippines, Puerto Rico and in Dubai. Only Australia, New Zealand and Iceland are reported to be free of the disease.

How is it carried
As in humans, the virus is inhaled affecting the airways and the respiratory tract. It is highly contagious amongst horses that are not innoculated. The incubation period is up to three days accompanied by high temperatures of about 41° C for a few days. The horse shows a lack of appetite, is depressed and shows a disinterest in surrounding activities. A deep dry cough becomes evident with a nasal discharge. Breathing can be affected for up to 32 days. Oedematous swellings may occur on the legs and scrotum. Colic has also been reported.

Complications
If pneumonia develops, the case usually becomes fatal. Pregnant mares may abort. Foals are highly at risk and death is more prevalent than with adults.

Management of an Influenza Outbreak
A normally healthy adult horse usually recovers within 10 days but coughing may continue. Box rest is essential and fresh water must always be available. Electrolytes in a separate bucket may be given. Veterinary treatment with non-steroidal anti-inflammatory drugs in cases of high fever is necessary and for pregnant mares, to reduce the risk of abortion. If secondary infection occurs, antibiotics should be administered. Quarantine horses to minimise the spread of the disease

There should be one week of complete rest for every day of elevated temperature and then a gradual return to work.

Vaccination
For adult horses an initial single dose is administered followed 3 – 6 weeks later by a second dose. 6 – 12 months after the second dose a booster is given followed by an annual booster which should be sufficient for older horses

For young horses, a) if the dam is vaccinated the initial single dose should be given at between 4 to 6 months of age when the maternal antibodies are at a minimum level or b) if the dam is unvaccinated the initial single dose should be given at about 3 months of age. 3 – 6 weeks after the initial dose in both cases the second dose is given. Thereafter it is recommended that the first booster be given after 3 months, the second booster after 6 months of the second dose and that continuing boosters are given at 6 monthly intervals for a few years

Avoid vaccinating horses two weeks prior to an event. Give a few days rest after vaccination. Broodmares should be vaccinated in the later stages of pregnancy but not within two weeks prior to foaling

Vaccines
Vaccines are usually composite containing representatives of both the American and European lineage of the virus. Some vaccines may contain tetanus antigens – do not administer anti-tetanus more frequently than manufacturers recommend.

Source material

In:  Equine Respiratory Diseases, Lekeux P. (Ed.) International Veterinary Information Service, Ithaca NY (www.ivis.org), 2001; B0322.1101

Influenza Infections  (Last Updated: 13-Nov-2001 ) J. M. Daly and J. A. Mumford Animal Health Trust, Lanwades Park, Kentford, Suffolk, Newmarket, UK.

All rights reserved. This document is available on-line at www.ivis.org. Document No. B0322.1101.

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